The present embodiments relate to solid phase change ink compositions characterized by being solid at room temperature and molten at an elevated temperature at which the molten ink is applied to a substrate. These solid ink compositions can be used for ink jet printing in a variety of applications. The present embodiments are directed to curable solid inks (CSI) and low shrinkage curable solid inks (LS-CSI) and methods of using the inks. In the present embodiments, the curable solid ink is an ultraviolet (UV) curable ink with significant hardness prior to cure, and a substantial increase in hardness after curing which is resistant to solvent rub. The present embodiments thus have a unique combination of characteristics that provide curable solid inks with both desirable uncured solid state properties as well improved properties in the cured state.
Ink jet printing processes generally may employ inks that are solid at room temperature and liquid at elevated temperatures. Such inks may be referred to as solid inks, hot melt inks, phase change inks and the like. For example, U.S. Pat. No. 4,490,731, the disclosure of which is totally incorporated herein by reference, discloses an apparatus for dispensing solid ink for printing on a recording medium such as paper. In thermal ink jet printing processes employing hot melt inks, the solid ink is melted by the heater in the printing apparatus and utilized (jetted) as a liquid in a manner similar to that of conventional thermal ink jet printing. Upon contact with the printing recording medium, the molten ink solidifies rapidly, allowing the colorant to substantially remain on the surface of the recording medium instead of being carried into the recording medium (for example, paper) by capillary action, thereby enabling higher print density than is generally obtained with liquid inks. Advantages of a solid ink in ink jet printing are thus elimination of potential spillage of the ink during handling, a wide range of print density and quality, minimal paper cockle or distortion, reduced print-through and enablement of indefinite periods of nonprinting without the danger of nozzle clogging, even without capping the nozzles.
Solid inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in solid ink jet printers wherein the ink droplets are applied directly onto the final recording medium (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the recording medium, so that migration of ink along the printing medium is prevented and dot quality is improved.
Curable solid inks were conceived as a means to use conventional solid ink print process, especially transfix, and deliver an increase in mechanical robustness after curing. One of the challenges in formulating a suitable curable solid ink is to create a solid ink with sufficient molecular mobility to allow rapid and extensive curing. Previous formulations have been disclosed in, such as for example, U.S. patent application Ser. No. 12/704,194 to Breton et al., which proposes use of an IGEPAL waxy derivative to increase cure speed. Reference is also made to U.S. application Ser. No. 12/642,538 to Breton et al., U.S. application Ser. No. 12/703,817 to Breton et al., and U.S. application Ser. No. 12/972,138 to Breton et al., the disclosures of which are totally incorporated herein by reference.
While the disclosed solid ink formulation provides some advantages over the prior formulations, there is still a need to achieve a formulation that provides a curable solid ink with more rapid and extensive curing and hardness. Thus, while the above conventional solid ink technology is generally successful in producing suitable solid inks, there is still a need for an improved curable solid ink that has increased curing speed and hardness after curing so that the resulting print is durable and can withstand much handling.
Each of the foregoing U.S. patents and patent Publications are incorporated by reference herein. Further, the appropriate components and process aspects of the each of the foregoing U.S. patents and patent Publications may be selected for the present disclosure in embodiments thereof.